Sewing machine

Abstract

Sewing machine includes a tension detection section ( 26 ) for detecting tension acting on a sewn material (A) paid out from a rotary holder member, and a drive section for driving the rotary holder member, and the driving operation of the drive section ( 14 ) is controlled on the basis of the detection by the tension detection section. Once the tension acting on the sewn material has increased, the rotary holder member is driven to rotate by the drive section, so that the sewn material can be paid out smoothly from the rotary holder member. The sewing machine is particularly useful in a case where the rotary holder member is constructed into an increased size so that an increased amount of the sewn material can be wound thereon.

1. A sewing machine including: a reciprocally-driven needle bar; a sewing needle fixed to a distal end of the needle bar; a rotary member provided concentrically with the needle bar for rotation about an axis of the needle bar; a rotary holder member having an elongated sewn material wound thereon; and a guide for guiding the sewn material, paid out from the rotary holder member, to a sewing position of the sewing needle, the guide being provided for rotation together with the rotary member, said sewing machine sewing the sewn material onto an object of sewing while adjusting an orientation of the guide by controlling the rotation of the rotary member, said sewing machine comprising:
 a tension detector that detects tension acting on the sewn material paid out from said rotary holder member; and 
 a drive device that drives said rotary holder member to rotate, driving operation of the drive device being controlled on the basis of detection, by said tension detector, of the tension. 
 
   
   
     2. A sewing machine as claimed in  claim 1  wherein said tension detector includes a displacement member mechanically displaceable in accordance with the tension acting on the sewn material, and a detector for detecting displacement of said displacement member. 
   
   
     3. A sewing machine as claimed in  claim 2  wherein said detector is a limit switch that is turned on or off in accordance with a displaced position of said displacement member or said deflection member. 
   
   
     4. A sewing machine as claimed in  claim 1  which further comprises a deflection member for changing a direction of the sewn material paid out from said rotary holder member, said deflection member is mechanically displaceable in accordance with the tension acting on the sewn material, and
 wherein said tension detector includes a detector for detecting displacement of said deflection member. 
 
   
   
     5. A sewing machine as claimed in  claim 4  wherein said detector is a limit switch that is turned on or off in accordance with a displaced position of said displacement member or said deflection member. 
   
   
     6. A sewing machine as claimed in  claim 1  wherein said drive device is activated when the tension acts on the sewn material, to drive said rotary holder member to rotate in a direction to pay out the sewn material. 
   
   
     7. A sewing machine as claimed in  claim 6  wherein said rotary holder member is a bobbin of a relatively large size positioned in a space above said needle bar. 
   
   
     8. A sewing machine as claimed in  claim 6  wherein the sewn material is a string material. 
   
   
     9. A sewing machine as claimed in  claim 1  wherein said rotary holder member is a bobbin of a relatively large size positioned in a space above said needle bar. 
   
   
     10. A sewing machine as claimed in  claim 1  wherein the sewn material is a string material.